The overall objective of this proposal is to discover novel therapy for the treatment of IPF. We propose two projects. The first project aims to determine the safety and efficacy of sirolimus combined with interferon gamma-1b (IFN-y lb) in 138 patients with idiopathic pulmonary fibrosis (IPF). We propose a two-year multi-center, randomized, double-blinded, controlled study of sirolimus plus IFN-y lb compared to IFN-y lb plus placebo in patients with IPF. Eligible patients will be randomly assigned, in a 2:1 ratio, to receive sirolimus plus IFN-y lb versus IFN-y lb plus placebo, respectively. Randomization will use a randomized permuted block design stratified by clinic with changing block sizes. The primary efficacy outcome is the 6-minute walk distance (6MWD). Secondary efficacy endpoints include pulmonary function, gas exchange, and quality of life (QOL). We hypothesize that patients with mild to moderate IPF (FVC >55% and DLCO >30% of predicted) will demonstrate stabilization or improvement in 6MWD over 96 weeks of treatment with combined therapy. The control group will be expected to demonstrate deterioration in 6MWD. The second project aims to determine the safety and efficacy of sildenafil in 100 patients with IPF and moderate pulmonary arterial hypertension (PAH;defined as meaning pulmonary arterial pressure >30 mm Hg at rest). We propose a 12-week multi-center, randomized, double-blinded, controlled study of sildenafil compared placebo in patients with IPF and PAH. Eligible patients will be equally randomized (1:1) into active or placebo groups. Randomization will use the permuted block design with stratification by clinic. The primary efficacy outcome is the 6MWD. Secondary efficacy endpoints include gas exchange and quality of life (QOL). We anticipate an improvement in 6MWD in patients who receive sildenafil compared to those who receive placebo. (End of Abstract)